Silicon-based light source represents a new path towards integrated, compact and mass manufacturable microsystems for advanced computing, networking, and sensing (Hirschman et al., Nature 384:338, 1996; Huang et al., Small 1-142, 2005; Rong et al., Nature 433:292, 2005). Silicon light emitting diodes (LEDs) have been demonstrated in the visible spectrum, using porous silicon (Hirschman et al., Nature 384-338, 1996) and most recently, multi-color emission from silicon nanowire (Huang et al., Small 1:142, 2005). It has also been demonstrated that silicon can be used as lasing material for optoelectronic integration with existing complementary metal oxide semiconductor (CMOS) circuitry (Rong et al., Nature 433:292, 2005). Integrated optical emitters also play a key role in silicon-based micrototal analysis systems for sensing and imaging (Hofmann et al., Lab Chip 5:863, 2005). New frontier of biological applications has also been demonstrated. Dislocation-based silicon light emitters, with emission wavelength 1.5 μm, have been used for manipulation of biomolecules (Kittler et al, Small 3:964, 2007). Nanoelectronic light emitting devices (Cui et al., Science 293:1289, 2001; Hafeman et al., Science 240:1182, 1988) incorporating silicon nanowires are emerging as highly sensitive, and real-time detectors of genes, mRNAs, and proteins. It was demonstrated a nano-scale light emitting diode (LED) created at the silicon probe tip (Hoshino et al., Appl. Phys. Lett. 92:131106, 2008; Hoshino et al., J. Microelectromech. Syst. 17:4, 2008), with the potential of near-field scanning optical imaging of nanodrug carrier distributions in biomaterials.
Several techniques have been proposed for silicon based LEDs. Some have been developed on bulk substrate using ion implantation at high doses typically followed by high-temperature annealing (Dekorsy et al., Appl. Phys. A 78:471, 2004). Others have been demonstrated, using porous silicon (Hirschman et al., Nature 384-338, 1996), silicon/silicon dioxide superlattice (Lu et al., Nature 378:258, 1995) and embedding silicon nanoparticles in silicon dioxide (Lalic and Linnros, J. Lumin. 80:263, 1998). However, silicon, being an indirect band gap material, is fundamentally a poor light emitter (Krames et al., J. Disp. Technol. 3:160, 2007).
Colloidal quantum dots, due to their unique tunable luminescence properties, have recently been studied as lumophores in light emitting devices on indium tin oxide (ITO) substrates (Anikeeva et al., Niano Lett. 7:2196, 2007; Colvin et al., Nature 370:354, 1994; Ray et al., J. Am. Chem. Soc. 128:8998, 1006). Nanoparticle based light emitting structures with integrated organic layers have shown improved external quantum efficiencies (Coe-Sullivan et al., Org. Electron. 4:123, 2003). Despite their high quantum efficiencies, these organic structures are susceptible to atmospheric conditions, moisture, thermal and electrochemical degradation Fenter et al., Chem. Phys. Lett. 277:521, 1997; Sato and Kanai, Mol. Cryst. Liq. Cryst. 253:143, 1994; Price et al., Small 3:372, 2007). It is hence desirable to have inorganic transport layers for robust LED structures compatible with existing electronics and sensors. Early work on inorganic LEDs had quantum dots sandwiched between either silver and ITO (Hikmet et al., J. Appl. Phys. 93:3509, 2003) or NiO and ZnO:SnO2 (Caruge et al., Nature 4:4.6, 2008). These LEDs have been developed on ITO substrates, which are not efficient in injecting holes to polymer layers, and an additional hole transporting layers is typically required. Described herein is a method for patterning QD-based light emitting devices (QD-LEDs) and the devices made by such techniques.